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I know O2 sensors are not that accurate, but I'm just looking for a target figue. I've logged my car and my friends MR and I'm getting .93-.94v on 91 octane. I know both cars are pretty much stock, run rich, and on his dyno A/F ratio he's getting 10.0(+):1. This is nothing like a 2G where the target O2's are .94-.95v. Is an Evo more like a 1G, in this area, where the target O2's are .89-.91 on 91 octane?
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http://www.roadraceengineering.com/instructions/autotimer.htm
 

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turbolarry said:
I know O2 sensors are not that accurate, but I'm just looking for a target figue. I've logged my car and my friends MR and I'm getting .93-.94v on 91 octane. I know both cars are pretty much stock, run rich, and on his dyno A/F ratio he's getting 10.0(+):1. This is nothing like a 2G where the target O2's are .94-.95v. Is an Evo more like a 1G, in this area, where the target O2's are .89-.91 on 91 octane?
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http://www.roadraceengineering.com/instructions/autotimer.htm

It seems like most people tuning an EVO do it on the dyno with a wide band, or road tune with a wide band.... I don't think many people have looked into using the narrow band stock sensor for tuning purposes due to the accuracy issues. In other words, I don't have any idea what the target voltage would be for an EVO.

If you or your friend get a flash, or tune on the dyno with a piggyback computer and log the stock O2 sensor voltage along with getting a printout of the A/F from the wideband on the dyno I think that is our only hope of finding out the anser to this question.

Keith
 

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.92 to .94 volts.
From Scott Gray regarding proper O2 range;

"the higher the narrowband voltage the richer the air/fuel mixture. So if .92 to .94 is okay, .96 is even richer.

The .92 to .94 range is listed as a range because the narrowband sensor is not super accurate and what one car likes may not be the same for another car. So .92 to .94 is a rule of thumb guide for what works for the majority of cars.

When tuning with an AFC, first get the O2 voltage stable across the whole RPM range at WOT, then if the EGTs are low like under 820C, reduce the AFC settings until the O2 voltage is stable again at a lower voltage.

For example, tune the AFC so the "curve" on the AFC results in the O2 voltage being flat across the whole RPM band at WOT with a target of .94. Then if the EGT is under control, reduce the target to .92 and see what happens with the EGT.
 
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